Selective material removal

ABSTRACT

Exemplary methods for removing nitride may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may further include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor and flowing the plasma effluents into a processing region of the semiconductor processing chamber housing a substrate. The substrate may include a high-aspect-ratio feature. The substrate may further include a region of exposed nitride and a region of exposed oxide. The methods may further include providing a hydrogen-containing precursor to the processing region to produce an etchant. At least a portion of the exposed nitride may be removed with the etchant.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment. More specifically, the present technology relates to selective etching of nitride and/or oxide materials.

BACKGROUND

Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge.

Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.

SUMMARY

Exemplary methods for selectively etching nitride materials may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may further include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor, and flowing the plasma effluents into a processing region of the semiconductor processing chamber. The processing region may house a substrate. The substrate may include a high-aspect-ratio feature. The substrate may further include a region of exposed silicon nitride and a region of exposed oxide. The methods may also include providing a hydrogen-containing precursor into the processing region of the semiconductor processing chamber. The methods may further include selectively removing at least a portion of the exposed silicon nitride relative to the exposed oxide.

In some embodiments, the hydrogen-containing precursor may bypass the remote plasma region when provided to the processing region. In some embodiments, the fluorine-containing precursor may include nitrogen trifluoride. In some embodiments, the hydrogen-containing precursor may include one of diatomic hydrogen or hydrogen fluoride. In some embodiments, the hydrogen-containing precursor may be oxygen-free. In some embodiments, a ratio of a flow rate of the fluorine-containing precursor to a flow rate of the hydrogen-containing precursor may range between about 1:10 and about 2:1. In some embodiments, a temperature of the substrate may be maintained between about 0° C. and about 150° C. during the etching method. In some embodiments, a pressure within the semiconductor processing chamber may be maintained between about 0.5 Torr and about 50 Torr. In some embodiments, the etching method may include a selectivity of silicon nitride to oxide greater than or about 500:1. In some embodiments, the etching method may produce a recessed sidewall of the exposed silicon nitride, and the recessed sidewall may include a substantially straight recess profile. In some embodiments, the exposed oxide may include silicon oxide. In some embodiments, the substrate may further include a region of exposed silicon. The portion of the exposed silicon nitride may be further selectively removed relative to the exposed silicon.

Further exemplary methods for selectively etching nitride materials may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may also include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may further include flowing the plasma effluents into a processing region of the semiconductor processing chamber. The processing region may house a substrate. The substrate may include a trench formed between two vertical columns. Each of the two vertical columns may include alternating layers of silicon nitride and an oxide material. In some embodiments, the methods may also include, while flowing the fluorine-containing precursor into the processing region, providing a hydrogen-containing precursor to the processing region to produce an etchant. The methods may further include selectively removing at least a portion of silicon nitride from each layer of silicon nitride with the etchant.

In some embodiments, a temperature of the substrate may be maintained between about 30° C. and about 85° C. during the etching method. In some embodiments, a pressure within the semiconductor processing chamber may be maintained between about 1 Torr and about 5 Torr. In some embodiments, a ratio of a flow rate of the fluorine-containing precursor to a flow rate of the hydrogen-containing precursor may be greater than or about 1:2. In some embodiments, the substrate may include a region of exposed silicon. The portion of silicon nitride from each layer of silicon nitride may be selectively removed relative to the exposed silicon. In some embodiments, the oxide material may include silicon oxide.

Further exemplary methods for selectively etching nitride materials may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may also include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may further include flowing a hydrogen-containing precursor into the remote plasma region of the semiconductor processing chamber. The methods may also include forming a plasma within the remote plasma region to generate plasma effluents of the hydrogen-containing precursor. The methods may further include flowing the plasma effluents of the fluorine-containing precursor and the plasma effluents of the hydrogen-containing precursor into a processing region of the semiconductor processing chamber. The processing region may house a substrate. The substrate may include a high-aspect-ratio feature. The substrate may further include a region of exposed silicon nitride and a region of exposed silicon oxide. The methods may further include selectively removing at least a portion of the exposed silicon nitride relative to the exposed silicon oxide. In some embodiments, the substrate may further include a region of exposed silicon, and wherein the portion of the exposed silicon nitride may be removed relative to the exposed silicon.

The present technology may provide numerous benefits over conventional techniques. The etch byproduct may be volatile and thus can be easily removed. Additionally, the present technology may allow for the capability of tuning the etched recess profile to achieve a convex, straight, and/or concave recess profile. The present technology can also achieve a much higher selectivity as compared to etching methods where oxide-containing precursors may be used. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplary processing system according to embodiments of the present technology.

FIG. 2 shows a cross-sectional view of an exemplary processing system.

FIG. 3 shows exemplary operations in a method according to some embodiments of the present technology.

FIGS. 4A and 4B show cross-sectional views of substrates being processed according to some embodiments of the present technology.

FIG. 5 shows exemplary operations in a method according to some embodiments of the present technology.

FIG. 6A shows the relationship between etch amounts and flow rates of precursors and the relationship between selectivity and flow rates of the precursors according to some embodiments of the present technology.

FIG. 6B shows the relationship between etch amount and etch time and the relationship between selectivity and etch time according to some embodiments of the present technology.

FIG. 6C shows the relationship between etch amounts and temperature and the relationship between selectivity and temperature according to some embodiments of the present technology.

FIGS. 7A and 7B show cross-sectional views of substrates being processed according to some embodiments of the present technology.

FIGS. 8A and 8B show the relationship between etch amounts and flow rates of precursors and the relationship between selectivity and flow rates of the precursors at different temperatures according to some embodiments of the present technology.

FIG. 9 shows the relationship between etch amounts and flow rates of precursors for various materials according to some embodiments of the present technology.

FIG. 10 shows exemplary operations in a method according to some embodiments of the present technology.

FIG. 11 shows the relationship between etch amount and etch time according to some embodiments of the present technology.

Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include exaggerated material for illustrative purposes.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.

DETAILED DESCRIPTION

The growing demands of mobile computing and data centers continue to drive the need for high-capacity, high-performance NAND flash technology. With planar NAND nearing the limits of practical scaling, 3D NAND is replacing 2D NAND for memory devices. Manufacturing 3D NAND structures may require depositing alternating layers of two or more materials, such as alternating layers of silicon oxide and silicon nitride, with a total thickness of the stacked layers up to several microns. These stacked layers may be etched to produce trenches or contact holes. Additionally, one of these two alternating materials, or at least a portion thereof, may be etched selectively from the trenches to form memory cells. As 3D NAND structures grow in the number of cells being formed, the aspect ratios of the trenches and other structures increase dramatically. Because of the high aspect ratio of the trenches, it has been challenging for conventional wet methods to uniformly etch the materials from top to bottom within the feature and to completely remove residual byproduct formed inside the feature. In addition, the recess profile of the material etched, such as silicon nitride, using a wet process can be convex and cannot be tuned or modulated. In some applications, a relatively straight recess profile may be desired. Dry etching using NF₃ and O₂ has also been explored for selectively etching nitride relative to oxide. However, the selectivity obtained by the conventional dry etching can be relatively low.

The present technology overcomes these issues by performing a dry etch process that allows uniform top to bottom etching of nitride materials inside trenches having high aspect ratios. The etch byproduct may be volatile and thus can be easily removed, leaving substantially no or less residual byproduct as compared to conventional wet methods. Further, the present technology may provide the capability of tuning the etched recess profile to achieve a convex, straight, and/or concave recess profile. The present technology can also achieve a much higher selectivity as compared to etching methods where oxide-containing precursors may be used.

Although the remaining disclosure will routinely identify specific etching processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to deposition and cleaning processes as may occur in the described chambers. Accordingly, the technology should not be considered to be so limited as for use with etching processes or chambers alone. Moreover, although an exemplary chamber is described to provide foundation for the present technology, it is to be understood that the present technology can be applied to virtually any semiconductor processing chamber that may allow the single-chamber operations described.

FIG. 1 shows a top plan view of one embodiment of a processing system 100 of deposition, etching, baking, and curing chambers according to embodiments. In the figure, a pair of front opening unified pods (FOUPs) 102 supply substrates of a variety of sizes that are received by robotic arms 104 and placed into a low pressure holding area 106 before being placed into one of the substrate processing chambers 108 a-f, positioned in tandem sections 109 a-c. A second robotic arm 110 may be used to transport the substrate wafers from the holding area 106 to the substrate processing chambers 108 a-f and back. Each substrate processing chamber 108 a-f, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation, and other substrate processes.

The substrate processing chambers 108 a-f may include one or more system components for depositing, annealing, curing and/or etching a dielectric film on the substrate wafer. In one configuration, two pairs of the processing chambers, e.g., 108 c-d and 108 e-f, may be used to deposit dielectric material on the substrate, and the third pair of processing chambers, e.g., 108 a-b, may be used to etch the deposited dielectric. In another configuration, all three pairs of chambers, e.g., 108 a-f, may be configured to etch a dielectric film on the substrate. Any one or more of the processes described may be carried out in chamber(s) separated from the fabrication system shown in different embodiments. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for dielectric films are contemplated by system 100.

FIG. 2 shows a schematic cross-sectional view of an exemplary processing system 200 according to embodiments of the present technology. System 200 may include a processing chamber 205 and a remote plasma unit 210. The remote plasma unit 210 may be coupled with processing chamber 205 with one or more components. The remote plasma unit 210 may be coupled with one or more of a remote plasma unit adapter 215, an isolator 220, a pressure plate 225, and inlet adapter 230, a diffuser 235, or a mixing manifold 240. Mixing manifold 240 may be coupled with a top of processing chamber 205, and may be coupled with an inlet to processing chamber 205.

Remote plasma unit adapter 215 may be coupled with remote plasma unit 210 at a first end 211, and may be coupled with isolator 220 at a second end 212 opposite first end 211. Through remote plasma unit adapter 215 may be defined one or more channels. At first end 211 may be defined an opening or port to a channel 213. Channel 213 may be centrally defined within remote plasma unit adapter 215, and may be characterized by a first cross-sectional surface area in a direction normal to a central axis through remote plasma unit adapter 215, which may be in the direction of flow from the remote plasma unit 210. A diameter of channel 213 may be equal to or in common with an exit port from remote plasma unit 210. Channel 213 may be characterized by a length from the first end 211 to the second end 212. Channel 213 may extend through the entire length of remote plasma unit adapter 215, or a length less than the length from first end 211 to second end 212. For example, channel 213 may extend less than halfway of the length from the first end 211 to the second end 212, channel 213 may extend halfway of the length from the first end 211 to the second end 212, channel 213 may extend more than halfway of the length from the first end 211 to the second end 212, or channel 213 may extend about halfway of the length from the first end 211 to the second end 212 of remote plasma unit adapter 215.

Remote plasma unit adapter 215 may also define one or more trenches 214 defined beneath remote plasma unit adapter 215. Trenches 214 may be or include one or more annular recesses defined within remote plasma unit adapter 215 to allow seating of an o-ring or elastomeric element, which may allow coupling with an isolator 220.

Isolator 220 may be coupled with second end 212 of remote plasma unit adapter 215 in embodiments. Isolator 220 may be or include an annular member about an isolator channel 221. Isolator channel 221 may be axially aligned with a central axis in the direction of flow through remote plasma unit adapter 215. Isolator channel 221 may be characterized by a second cross-sectional area in a direction normal to a direction of flow through isolator 220. The second cross-sectional area may be equal to, greater than, or less than the first cross-sectional area of channel 213. In embodiments, isolator channel 221 may be characterized by a diameter greater than, equal to, or about the same as a diameter of channel 213 through remote plasma unit adapter 215.

Isolator 220 may be made of a similar or different material from remote plasma unit adapter 215, mixing manifold 240, or any other chamber component. In some embodiments, while remote plasma unit adapter 215 and mixing manifold 240 may be made of or include aluminum, including oxides of aluminum, treated aluminum on one or more surfaces, or some other material, isolator 220 may be or include a material that is less thermally conductive than other chamber components. In some embodiments, isolator 220 may be or include a ceramic, plastic, or other thermally insulating component configured to provide a thermal break between the remote plasma unit 210 and the chamber 205. During operation, remote plasma unit 210 may be cooled or operate at a lower temperature relative to chamber 205, while chamber 205 may be heated or operate at a higher temperature relative to remote plasma unit 210. Providing a ceramic or thermally insulating isolator 220 may prevent or limit thermal, electrical, or other interference between the components.

Coupled with isolator 220 may be a pressure plate 225. Pressure plate 225 may be or include aluminum or another material in embodiments, and pressure plate 225 may be made of or include a similar or different material than remote plasma unit adapter 215 or mixing manifold 240 in embodiments. Pressure plate 225 may define a central aperture 223 through pressure plate 225. Central aperture 223 may be characterized by a tapered shape through pressure plate 225 from a portion proximate isolator channel 221 to the opposite side of pressure plate 225. A portion of central aperture 223 proximate isolator channel 221 may be characterized by a cross-sectional area normal a direction of flow equal to or similar to a cross-sectional area of isolator channel 221. Central aperture 223 may be characterized by a percentage of taper of greater than or about 10% across a length of pressure plate 225, and may be characterized by a percentage of taper greater than or about 20%, greater than or about 30%, greater than or about 40%, greater than or about 50%, greater than or about 60%, greater than or about 70%, greater than or about 80%, greater than or about 90%, greater than or about 100%, greater than or about 150%, greater than or about 200%, greater than or about 300%, or greater in embodiments. Pressure plate 225 may also define one or more trenches 224 defined beneath isolator 220. Trenches 224 may be or include one or more annular recesses defined within pressure plate 225 to allow seating of an o-ring or elastomeric element, which may allow coupling with isolator 220.

An inlet adapter 230 may be coupled with pressure plate 225 at a first end 226, and coupled with diffuser 235 at a second end 227 opposite first end 226. Inlet adapter 230 may define a central channel 228 defined through inlet adapter 230. Central channel 228 may be characterized by a first portion 229 a, and a second portion 229 b. First portion 229 a may extend from first end 226 to a first length through inlet adapter 230, wherein central channel 228 may transition to second portion 229 b, which may extend to second end 227. First portion 229 a may be characterized by a first cross-sectional area or diameter, and second portion 229 b may be characterized by a second cross-sectional area or diameter less than the first. In embodiments the cross-sectional area or diameter of first portion 229 a may be twice as large as the cross-sectional area or diameter of second portion 229 b, and may be up to or greater than about three times as large, greater than or about 4 times as large, greater than or about 5 times as large, greater than or about 6 times as large, greater than or about 7 times as large, greater than or about 8 times as large, greater than or about 9 times as large, greater than or about 10 times as large, or greater in embodiments. Central channel 228 may be configured to provide plasma effluents of a precursor delivered from remote plasma unit 210 in embodiments, which may pass through channel 213 of remote plasma unit adapter 215, isolator channel 221 of isolator 220, and central aperture 223 of pressure plate 225.

Inlet adapter 230 may also define one or more second channels 231, which may extend from below first portion 229 a to or through second end 227. The second channels 231 may be characterized by a second cross-sectional surface area in a direction normal to the central axis through inlet adapter 230. The second cross-sectional surface area may be less than the cross-sectional surface area of first portion 229 a in embodiments, and may be greater than the cross-sectional surface area or a diameter of second portion 229 b. Second channels 231 may extend to an exit from inlet adapter 230 at second end 227, and may provide egress from adapter 230 for a precursor, such as a first bypass precursor, delivered alternately from the remote plasma unit 210. For example, second channel 231 may be fluidly accessible from a first port 232 defined along an exterior surface, such as a side, of inlet adapter 230, which may bypass remote plasma unit 210. First port 232 may be at or below first portion 229 a along a length of inlet adapter 230, and may be configured to provide fluid access to the second channel 231.

Second channel 231 may deliver the precursor through the inlet adapter 230 and out second end 227. Second channel 231 may be defined in a region of inlet adapter 230 between first portion 229 a and second end 227. In embodiments, second channel 231 may not be accessible from central channel 228. Second channel 231 may be configured to maintain a precursor fluidly isolated from plasma effluents delivered into central channel 228 from remote plasma unit 210. The first bypass precursor may not contact plasma effluents until exiting inlet adapter 230 through second end 227. Second channel 231 may include one or more channels defined in adapter 230. Second channel 231 may be centrally located within adapter 230, and may be associated with central channels 228. For example, second channel 231 may be concentrically aligned and defined about central channel 228 in embodiments. Second channel 231 may be an annular or cylindrical channel extending partially through a length or vertical cross-section of inlet adapter 230 in embodiments. In some embodiments, second channel 231 may also be a plurality of channels extending radially about central channel 228.

Inlet adapter 230 may also define one or more third channels 233, which may extend from below first portion 229 a to or through second end 227, and may extend from below a plane bisecting first port 232. The third channels 233 may be characterized by a third cross-sectional surface area in a direction normal to the central axis through inlet adapter 230. The third cross-sectional surface area may be less than the cross-sectional surface area of first portion 229 a in embodiments, and may be greater than the cross-sectional surface area or a diameter of second portion 229 b. The third cross-sectional surface area may also be equal to or similar to the cross-sectional surface area or a diameter of first portion 229 a as illustrated. For example, an outer diameter of third channel 233 may be equivalent to an outer diameter of first portion 229 a, or may be less than an outer diameter of first portion 229 a. Third channels 233 may extend to an exit from inlet adapter 230 at second end 227, and may provide egress from adapter 230 for a precursor, such as a second bypass precursor, delivered alternately from the remote plasma unit 210. For example, third channel 233 may be fluidly accessible from a second port 234 defined along an exterior surface, such as a side, of inlet adapter 230, which may bypass remote plasma unit 210. Second port 234 may be located on an opposite side or portion of inlet adapter 230 as first port 232. Second port 234 may be at or below first portion 229 a along a length of inlet adapter 230, and may be configured to provide fluid access to the third channel 233. Second port 234 may also be at or below first port 232 along a length of inlet adapter 230 in embodiments.

Third channel 233 may deliver the second bypass precursor through the inlet adapter 230 and out second end 227. Third channel 233 may be defined in a region of inlet adapter 230 between first portion 229 a and second end 227. In embodiments, third channel 233 may not be accessible from central channel 228. Third channel 233 may be configured to maintain a second bypass precursor fluidly isolated from plasma effluents delivered into central channel 228 from remote plasma unit 210, and from a first bypass precursor delivered into second channel 231 through first port 232. The second bypass precursor may not contact plasma effluents or a first bypass precursor until exiting inlet adapter 230 through second end 227. Third channel 233 may include one or more channels defined in adapter 230. Third channel 233 may be centrally located within adapter 230, and may be associated with central channels 228 and second channel 231. For example, third channel 233 may be concentrically aligned and defined about central channel 228 in embodiments, and may be concentrically aligned and defined about second channel 231. Third channel 233 may be a second annular or cylindrical channel extending partially through a length or vertical cross-section of inlet adapter 230 in embodiments. In some embodiments, third channel 233 may also be a plurality of channels extending radially about central channel 228.

Diffuser 235 may be positioned between inlet adapter 230 and mixing manifold 240 to maintain precursors delivered through inlet adapter 230 fluidly isolated until accessing mixing manifold 240. Diffuser 235 may be characterized by one or more channels, such as cylindrical or annular channels defined through diffuser 235. In embodiments, diffuser 235 may define a first channel 236 or central channel, a second channel 237, and a third channel 238. The channels may be characterized by similar dimensions or diameters as second portion 229 b of central channel 228, second channel 231, and third channel 233 of inlet adapter 230. For example, each channel may extend the inlet adapter channels to mixing manifold 240. Second channel 237 and third channel 238 may each be annular channels defined about first channel 236, and first channel 236, second channel 237, and third channel 238 may be concentrically aligned in embodiments and defined through diffuser 235.

Diffuser 235 may additionally define one or more trenches 239 about diffuser 235. For example, diffuser 235 may define a first trench 239 a, a second trench 239 b, and a third trench 239 c in embodiments, which may allow seating of o-rings or elastomeric members between inlet adapter 230 and diffuser 235. Each of trenches 239 may be an annular trench in embodiments that sits radially exterior to one or more of the channels defined through diffuser 235. First trench 239 a may be located radially outward of first channel 236, and may be located between first channel 236 and second channel 237. Second trench 239 b may be located radially outward of second channel 237, and may be located between second channel 237 and third channel 238. Third trench 239 c may be located radially outward of third channel 238. A diameter of each trench 239 may be greater than the channel to which it may be associated and to which it may be located radially exterior. The trenches may enable improved sealing between the inlet adapter 230 and the diffuser 235 to ensure precursors are maintained fluidly isolated between the components, and leaking between the channels does not occur.

Mixing manifold 240 may be coupled with diffuser 235 at a first end 241, and may be coupled with chamber 205 at a second end 242. Mixing manifold 240 may define an inlet 243 at first end 241. Inlet 243 may provide fluid access from diffuser 235, and inlet 243 may be characterized by a diameter equal to or about the same as a diameter of third channel 238 through diffuser 235. Inlet 243 may define a portion of a channel 244 through mixing manifold 240, and the channel 244 may be composed of one or more sections defining a profile of channel 244. Inlet 243 may be a first section in the direction of flow through channel 244 of mixing manifold 240. Inlet 243 may be characterized by a length that may be less than half a length in the direction of flow of mixing manifold 240. The length of inlet 243 may also be less than a third of the length of mixing manifold 240, and may be less than one quarter the length of mixing manifold 240 in embodiments. Inlet 243 may receive each precursor from diffuser 235, and may allow for mixing of the precursors, which may have been maintained fluidly isolated until delivery to mixing manifold 240.

Inlet 243 may extend to a second section of channel 244, which may be or include a tapered section 245. Tapered section 245 may extend from a first diameter equal to or similar to a diameter of inlet 243 to a second diameter less than the first diameter. In some embodiments, the second diameter may be about or less than half the first diameter. Tapered section 245 may be characterized by a percentage of taper of greater than or about 10%, greater than or about 20%, greater than or about 30%, greater than or about 40%, greater than or about 50%, greater than or about 60%, greater than or about 70%, greater than or about 80%, greater than or about 90%, greater than or about 100%, greater than or about 150%, greater than or about 200%, greater than or about 300%, or greater in embodiments.

Tapered section 245 may transition to a third region of channel 244, which may be a flared section 246. Flared section 246 may extend from tapered section 245 to an outlet of mixing manifold 240 at second end 242. Flared section 246 may extend from a first diameter equal to the second diameter of tapered section 245 to a second diameter greater than the first diameter. In some embodiments, the second diameter may be about or greater than double the first diameter. Flared section 246 may be characterized by a percentage of flare of greater than or about 10%, greater than or about 20%, greater than or about 30%, greater than or about 40%, greater than or about 50%, greater than or about 60%, greater than or about 70%, greater than or about 80%, greater than or about 90%, greater than or about 100%, greater than or about 150%, greater than or about 200%, greater than or about 300%, or greater in embodiments.

Flared section 246 may provide egress to precursors delivered through mixing manifold 240 through second end 242 via an outlet 247. The sections of channel 244 through mixing manifold 240 may be configured to provide adequate or thorough mixing of precursors delivered to the mixing manifold, before providing the mixed precursors into chamber 205. Unlike conventional technology, by performing the etchant or precursor mixing prior to delivery to a chamber, the present systems may provide an etchant having uniform properties prior to being distributed about a chamber and substrate. In this way, processes performed with the present technology may have more uniform results across a substrate surface.

Chamber 205 may include a number of components in a stacked arrangement. The chamber stack may include a gasbox 250, a blocker plate 260, a faceplate 270, an ion suppression element 280, and a lid spacer 290. The components may be utilized to distribute a precursor or set of precursors through the chamber to provide a uniform delivery of etchants or other precursors to a substrate for processing. In embodiments, these components may be stacked plates each at least partially defining an exterior of chamber 205.

Gasbox 250 may define a chamber inlet 252. A central channel 254 may be defined through gasbox 250 to deliver precursors into chamber 205. Inlet 252 may be aligned with outlet 247 of mixing manifold 240. Inlet 252 and/or central channel 254 may be characterized by a similar diameter in embodiments. Central channel 254 may extend through gasbox 250 and be configured to deliver one or more precursors into a volume 257 defined from above by gasbox 250. Gasbox 250 may include a first surface 253, such as a top surface, and a second surface 255 opposite the first surface 253, such as a bottom surface of gasbox 250. Top surface 253 may be a planar or substantially planar surface in embodiments. Coupled with top surface 253 may be a heater 248.

Heater 248 may be configured to heat chamber 205 in embodiments, and may conductively heat each lid stack component. Heater 248 may be any kind of heater including a fluid heater, electrical heater, microwave heater, or other device configured to deliver heat conductively to chamber 205. In some embodiments, heater 248 may be or include an electrical heater formed in an annular pattern about first surface 253 of gasbox 250. The heater may be defined across the gasbox 250, and around mixing manifold 240. The heater may be a plate heater or resistive element heater that may be configured to provide up to, about, or greater than about 2,000 W of heat, and may be configured to provide greater than or about 2,500 W, greater than or about 3,000 W, greater than or about 3,500 W, greater than or about 4,000 W, greater than or about 4,500 W, greater than or about 5,000 W, or more.

Heater 248 may be configured to produce a variable chamber component temperature up to, about, or greater than about 50° C., and may be configured to produce a chamber component temperature greater than or about 75° C., greater than or about 100° C., greater than or about 150° C., greater than or about 200° C., greater than or about 250° C., greater than or about 300° C., or higher in embodiments. Heater 248 may be configured to raise individual components, such as the ion suppression element 280, to any of these temperatures to facilitate processing operations, such as an anneal. In some processing operations, a substrate may be raised toward the ion suppression element 280 for an annealing operation, and heater 248 may be adjusted to conductively raise the temperature of the heater to any particular temperature noted above, or within any range of temperatures within or between any of the stated temperatures.

Second surface 255 of gasbox 250 may be coupled with blocker plate 260. Blocker plate 260 may be characterized by a diameter equal to or similar to a diameter of gasbox 250. Blocker plate 260 may define a plurality of apertures 263 through blocker plate 260, only a sample of which are illustrated, which may allow distribution of precursors, such as etchants, from volume 257, and may begin distributing precursors through chamber 205 for a uniform delivery to a substrate. Although only a few apertures 263 are illustrated, it is to be understood that blocker plate 260 may have any number of apertures 263 defined through the structure. Blocker plate 260 may be characterized by a raised annular section 265 at an external diameter of the blocker plate 260, and a lowered annular section 266 at an external diameter of the blocker plate 260. Raised annular section 265 may provide structural rigidity for the blocker plate 260, and may define sides or an external diameter of volume 257 in embodiments. Blocker plate 260 may also define a bottom of volume 257 from below. Volume 257 may allow distribution of precursors from central channel 254 of gasbox 250 before passing through apertures 263 of blocker plate 260. Lowered annular section 266 may also provide structural rigidity for the blocker plate 260, and may define sides or an external diameter of a second volume 258 in embodiments. Blocker plate 260 may also define a top of volume 258 from above, while a bottom of volume 258 may be defined by faceplate 270 from below.

Faceplate 270 may include a first surface 272 and a second surface 274 opposite the first surface 272. Faceplate 270 may be coupled with blocker plate 260 at first surface 272, which may engage lowered annular section 266 of blocker plate 260. Faceplate 270 may define a ledge 273 at an interior of second surface 274, extending to third volume 275 at least partially defined within or by faceplate 270. For example, faceplate 270 may define sides or an external diameter of third volume 275 as well as a top of volume 275 from above, while ion suppression element 280 may define third volume 275 from below. Faceplate 270 may define a plurality of channels through the faceplate, although not illustrated in FIG. 2.

Ion suppression element 280 may be positioned proximate the second surface 274 of faceplate 270, and may be coupled with faceplate 270 at second surface 274. Ion suppression element 280 may be configured to reduce ionic migration into a processing region of chamber 205 housing a substrate. Ion suppression element 280 may define a plurality of apertures through the structure, although not illustrated in FIG. 2. In embodiments, gasbox 250, blocker plate 260, faceplate 270, and ion suppression element 280 may be coupled together, and in embodiments may be directly coupled together. By directly coupling the components, heat generated by heater 248 may be conducted through the components to maintain a particular chamber temperature that may be maintained with less variation between components. Ion suppression element 280 may also contact lid spacer 290, which together may at least partially define a plasma processing region in which a substrate is maintained during processing.

The chamber discussed previously may be used in performing exemplary methods including etching methods. FIG. 3 shows exemplary operations in a method 300 according to embodiments of the present technology. Prior to the first operation of the method 300, a substrate, which may include a silicon substrate, may be processed in one or more ways. For example, films or layers may be deposited, grown, or otherwise formed on the substrates. Features, such as trenches, holes, or other features may be formed in the films or layers on the substrate. FIG. 4A illustrates a portion of such a processed structure 400. The processed structure 400 may include one or more trenches 405 (only one shown) formed between adjacent vertical columns 410 of stacked layers overlying a substrate 415. The stacked layers may include dielectric layers, which may include alternating layers of oxide and nitride, such as alternating layers of silicon oxide 420 and layers of silicon nitride 425 as shown in FIG. 4A. The substrate 415 may include a silicon substrate. One of these two alternating materials, or at least a portion thereof, may be etched selectively from the trenches to produce, for example, 3D NAND structures, or any other semiconductor structures. Although FIG. 4A illustrates only four layers of silicon oxide 420 and three layers of silicon nitride 425, the processed structure 400 may include any number of layers of each material, such as up to or greater than about 10, greater than or about 15, greater than or about 20, greater than or about 25, greater than or about 30, greater than or about 35, greater than or about 40, greater than or about 45, greater than or about 50, greater than or about 55, greater than or about 60, greater than or about 65, greater than or about 70, greater than or about 80, greater than or about 90, greater than or about 100, or more layers of each material. This may produce trenches 405 with a width of a few tens of nanometers or less, while the height thereof may be on the order of a few microns or more. The resulting aspect ratios or height to width ratios of the trenches 405 may be greater than 20:1, greater than 40:1, greater than 75:1, greater than 100:1, or even greater. In some embodiments, the processed structure 400 may be produced in the same processing chamber as the processing chamber in which method 300 may be performed, or may be produced in a different processing chamber and then transferred to the processing chamber in which method 300 may be performed.

Once the processed structure 400 may be positioned within a processing region of a semiconductor processing chamber housing the processed structure 400, method 300 may be initiated by flowing a halogen-containing precursor into a remote plasma region of the semiconductor processing chamber at operation 305. An exemplary processing chamber may be chamber 205 previously described, which may include one or both of the RPS unit 210 or a plasma region within the chamber that may be fluidly coupled with the processing region, but may be physically partitioned to limit plasma at the substrate level. Either or both of these regions may be the remote plasma region used in operation 305. A plasma may be generated within the remote plasma region at operation 310, which may generate plasma effluents of the halogen-containing precursor. The plasma effluents may be flowed to the processing region of the chamber at operation 315. At operation 320, a hydrogen-containing precursor may be provided to the processing region along with the plasma effluents. At operation 325, the plasma effluents and the hydrogen-containing precursor may modify and interact with the exposed silicon nitride 425 to form volatile substances, such as ammonium fluorosilicate, which may then be removed from the chamber. In some embodiments, the plasma effluents and the hydrogen-containing precursor may not react with the exposed silicon oxide 420 or the reaction may be limited. Accordingly, method 300 may selectively remove the exposed silicon nitride 425 relative to the exposed silicon oxide 420, forming lateral recesses or recessed sidewalls 430 in the layers of the silicon nitride 425, as shown in FIG. 4B.

In some embodiments, such as method 300, the hydrogen-containing precursor may bypass the remote plasma region. Specifically, while the halogen-containing precursor may be flowed through the remote plasma region to produce plasma effluents of the halogen-containing precursor, the hydrogen-containing precursor may bypass the remote plasma region. The hydrogen-containing precursor may bypass the remote plasma region by a bypass at a top of the chamber, or may be flowed into a region of the chamber separate from the remote plasma region. The hydrogen-containing precursor may then be mixed with the plasma effluents in the processing region or some other region of the chamber. In some embodiments, the plasma effluents of the halogen-containing precursor and the hydrogen-containing precursor may be delivered into a mixing manifold, such as the mixing manifold 240 described above, to achieve adequate or thorough mixing before being provided into the processing region of the chamber.

With reference to FIG. 5, exemplary operations in another method 500 according to embodiments of the present technology are shown. Method 500 is similar to method 300 except that the hydrogen-containing precursor may also be flowed into the remote plasma region of the processing chamber. Specifically, once the processed structure 400 may be positioned within the processing region of the processing chamber, method 500 may be initiated by flowing a halogen-containing precursor into the remote plasma region of the processing chamber at operation 505. At operation 510, a hydrogen-containing precursor may be flowed into the remote plasma region. At operation 515, a plasma may be generated within the remote plasma region, which may generate plasma effluents of the halogen-containing precursor and plasma effluents of the hydrogen-containing precursor. The plasma effluents may be flowed to the processing region of the chamber at operation 520. At operation 525, the plasma effluents of the halogen-containing precursor and the plasma effluents of the hydrogen-containing precursor may modify and interact with the exposed silicon nitride 425 to form volatile substances, such as ammonium fluorosilicate, which may then be removed from the chamber. Similar to the combination of the plasma effluents of the halogen-containing precursor and the hydrogen-containing precursor of method 300, the combined plasma effluents of the halogen-containing precursor and the plasma effluents of the hydrogen-containing precursor of method 500 may not react with the exposed silicon oxide 420 or the reaction may be limited. Accordingly, method 500 may selectively remove the exposed silicon nitride 425 relative to the exposed silicon oxide 420, forming the recessed sidewalls 430 in the layers of silicon nitride 425.

The halogen-containing precursor used in method 300 and/or method 500 may include a fluorine-containing precursor. An exemplary fluorine-containing precursor may be nitrogen trifluoride (NF₃). Other sources of fluorine may be used in conjunction with or as replacements for nitrogen trifluoride. In some embodiments, the fluorine-containing precursor may include at least one precursor selected from the group of atomic fluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride, hydrogen fluoride, xenon difluoride, and various other fluorine-containing precursors used or useful in semiconductor processing. The precursor may also include any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful gases.

The hydrogen-containing precursor used in method 300 and/or method 500 may include diatomic hydrogen (H₂) or hydrogen fluoride (HF). Other sources of hydrogen may be used in conjunction with or as replacements for hydrogen and/or hydrogen fluoride. In some embodiments, the hydrogen-containing precursor may include at least one precursor selected from the group of diatomic hydrogen, hydrogen fluoride, a hydrocarbon, an alcohol, hydrogen peroxide, and various other hydrogen-containing containing precursors used or useful in semiconductor processing. In some embodiments, the hydrogen-containing precursor may not include oxygen or may be oxygen-free. When the hydrogen-containing precursor may be oxygen-free, flowing the hydrogen-containing precursor into the processing chamber may not introduce a source of oxygen into the processing chamber. By eliminating oxygen, some embodiments may achieve a significantly higher selectivity that may not be achieved by precursors containing oxygen. As will be discussed below, the present technology may achieve a selectivity of silicon nitride to silicon oxide greater than or about 100:1, greater than or about 200:1, greater than or about 300:1, greater than or about 400:1, greater than or about 500:1, greater than or about 600:1, greater than or about 700:1, greater than or about 800:1, or greater. The precursor may also include any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful gases.

The halogen-containing precursor and the hydrogen-containing precursor may be flowed at a similar rate or may be flowed at different rates. The halogen-containing precursor and/or the hydrogen-containing precursor may be flowed at a rate of at least 10 sccm, and may be flowed at a rate greater than or about 20 sccm, greater than or about 40 sccm, greater than or about 60 sccm, greater than or about 80 sccm, greater than or about 100 sccm, greater than or about 120 sccm, greater than or about 140 sccm, greater than or about 160 sccm, greater than or about 180 sccm, greater than or about 200 sccm, greater than or about 220 sccm, greater than or about 240 sccm, greater than or about 260 sccm, greater than or about 280 sccm, greater than or about 300 sccm, greater than or about 350 sccm, greater than or about 400 sccm, greater than or about 500 sccm, greater than or about 600 sccm, greater than or about 700 sccm, greater than or about 800 sccm, greater than or about 900 sccm, greater than or about 1000 sccm, greater than or about 1200 sccm, greater than or about 1400 sccm, greater than or about 1600 sccm, greater than or about 1800 sccm, greater than or about 2000 sccm, or more in embodiments. A ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor may be at least about 1:10, and may be greater than or about 1:9, greater than or about 1:8, greater than or about 1:7, greater than or about 1:6, greater than or about 1:5, greater than or about 1:4, greater than or about 1:3, greater than or about 1:2, greater than or about 1:1, greater than or about 2:1, or greater in various embodiments.

By adjusting the flow rate of the halogen-containing precursor and/or the flow rate of the hydrogen-containing precursor, and/or by adjusting the ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor, a high selectivity of silicon nitride to silicon oxide may be achieved. FIG. 6A illustrates the relationship between the etch amounts and the flow rates of the precursors and the relationship between the selectivity and the flow rates of the precursors. Because the precursors were flowed for a similar period of time for each data point collected, FIG. 6A may also reflect the relationship between the etch rates and the flow rates of the precursors. In the embodiment shown in FIG. 6A, the halogen-containing precursor includes nitrogen trifluoride, and the hydrogen-containing precursor includes diatomic hydrogen, although similar trends or relationships may be observed when other halogen-containing precursors or other hydrogen-containing precursors, such as hydrogen fluoride, may be used. In some embodiments, the exposed silicon nitride may include plasma enhanced silicon nitride, such as silicon nitride deposited using plasma enhanced chemical vapor deposition, plasma enhanced atomic layer deposition, or other plasma enhanced deposition techniques. Plasma enhanced silicon nitride may be typically used for producing 3D NAND structures. In some embodiments, the exposed silicon nitride may include low pressure silicon nitride, such as silicon nitride deposited using low pressure chemical vapor deposition. Compared to plasma enhanced silicon nitride, low pressure silicon nitride may include a greater density and/or strength, and/or a lesser amount of impurities in the film deposited. In some embodiments, the exposed silicon nitride may include silicon nitrides deposited using atomic layer deposition (ALD) at various temperatures. The exposed silicon oxide may include thermal oxide. Although plasma enhanced silicon nitride, lower pressure silicon nitride, silicon nitride deposited using ALD, and thermal oxide are described herein as examples, the present technology may selectively etch other types of silicon nitride relative to thermal oxide or other types of silicon oxide.

The flow rate of the halogen-containing precursor and/or the hydrogen-containing precursor may be maintained between about 10 sccm and about 2000 sccm. The ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor may range between about 1:5 and about 1:1 or may be greater than 1:1. In some embodiments, when the flow rate of the halogen-containing precursor may be increased, or when the ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor may be increased from about 1:5 to about 1:2, the amount of plasma effluents of the halogen-containing precursor flowed into the processing region where the substrate may be housed may be increased. As the amount of plasma effluents may be increased, available etchants may also increase, and the etch amounts and/or etch rates for both of silicon nitride and silicon oxide may increase.

When the halogen-containing precursor may be flowed at increasing flow rates, or when the ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor may be about 1:2 or greater, the etch amounts and/or etch rates for both of silicon nitride and silicon oxide may decrease. Without intending to be bound to any particular theory, the decrease in the etch amounts and/or etch rates for silicon oxide and silicon oxide may be due to the increased flow rate ratio of the halogen-containing precursor to the hydrogen-containing precursor. Specifically, although the amount of the plasma effluents of the halogen-containing precursor may be increased, the overall amount of etchants, including ammonium fluoride that may be formed from the plasma effluents and the hydrogen-containing precursor, may be reduced when the flow rate ratio may be increased to be greater than or about 1:2. However, the decrease in the etch amount and/or etch rate of silicon oxide may be more significant than the decrease in the etch amount and/or etch rate of silicon nitride. As shown in FIG. 6A, when the flow rate ratio may be further increased to about 1:1, the etching of silicon oxide may be substantially suppressed, whereas the etching of silicon nitride may still be sustained.

Because the etching of silicon oxide may decrease more significantly than the etching of silicon nitride, or may be substantially suppressed when the flow rate ratio of the halogen-containing precursor to the hydrogen-containing precursor may be increased from about 2:1 to about 1:1 or greater, a very high selectivity of silicon nitride to silicon oxide may be achieved. In some embodiments, the present technology may achieve a selectivity of silicon nitride to silicon oxide greater than or about 100:1, greater than or about 200:1, greater than or about 300:1, greater than or about 400:1, greater than or about 500:1, greater than or about 600:1, greater than or about 700:1, greater than or about 800:1, or greater. Even when the flow rate ratio of halogen-containing precursor to the hydrogen-containing precursor may be maintained at about 1:2 or less, the present technology may still selectively etch silicon nitride relative to silicon oxide, achieving a selectivity greater than 1:1, greater than or about 1.2:1, greater than or about 1.4:1, greater than or about 1.6:1, greater than or about 1.8:1, greater than or about 2:1, greater than or about 3:1, greater than or about 4:1, greater than or about 5:1, greater than or about 6:1, greater than or about 7:1, greater than or about 8:1, greater than or about 9:1, greater than or about 10:1, or greater. In other words, the methods described herein may selectively etch silicon nitride relative to silicon oxide whether the flow rate of the halogen-containing precursor may be less than, similar to or substantially the same as, or greater than the flow rate of the hydrogen-containing precursor. Accordingly, depending on the particular application, the flow rates of the halogen-containing precursor and/or the hydrogen-containing precursor and/or the flow rate ratio may be modulated to achieve high selectivity, high etch amount or etch rate, conservation of the precursors, etc., or a balance or combination thereof.

In addition to the capability of achieving high selectivity, the methods described herein may also maintain the etch rate of silicon nitride with time. As shown in FIG. 6B, the etch amount of silicon nitride may increase over time, and in some embodiments, the etch amount of silicon nitride may be substantially linearly dependent on etch time. In other words, the etch rate of silicon nitride may be sustained over time and may not decrease as the etching operations may be continued. Furthermore, the methods described herein may substantially suppress the etching of silicon oxide as the etching of silicon nitride may be continued, unlike some conventional etching methods where the etching of silicon oxide or other materials to be preserved may nonetheless occur and may even increase over time. Consequently, the selectivity of those conventional etching methods may not be sustained and may decrease over time. In contrast, the methods described herein may maintain the selectivity of silicon nitride to silicon oxide and other materials to be preserved over time and the selectivity of silicon nitride may not decrease over time as is also shown FIG. 6B.

Process conditions may also impact the operations performed in methods 300 or 500 as well as other removal methods according to the present technology. A temperature within the processing chamber or at the substrate level may be maintained between about −10° C. or lower and about 200° C. or higher in embodiments. For example, in some embodiments, the processing temperature may be maintained between about 0° C. and about 150° C., between about 10° C. and about 125° C., between about 20° C. and about 100° C., between about 30° C. and about 85° C., between about 40° C. and about 80° C., between about 50° C. and about 75° C., or between about 60° C. and about 70° C.

FIG. 6C illustrates the relationship between the etch amounts and the temperature and the relationship between the selectivity and the temperature. Because the precursors were flowed for a similar period of time for each data point collected, FIG. 6C may also reflect the relationship between the etch rates and the flow rates of the precursors. As shown in FIG. 6C, the etch amount and/or etch rate of the silicon nitride may gradually increase as the temperature within the processing chamber may be gradually increased from 0° C. or below to a temperature between about 30° C. and about 85° C. However, the etch amount and/or etch rate of the silicon nitride may not increase, or may decrease as the temperature may continue to increase. As is also shown in FIG. 6C, the method may selectively etch silicon nitride relative to the silicon oxide within the entire operating range of the temperature, although the selectivity may vary at different temperatures, similar to how the etch amount and/or etch rate of the silicon nitride may vary at different temperatures.

Without intending to be bound to any particular theory, when the temperature may gradually increase from 0° C. or below to a temperature between about 30° C. and about 85° C., the etchants may obtain more energy to reach the substrate to be adsorbed on the substrate surface and react with the structure to be etched. As more etchants may be adsorbed on the substrate surface, the etch amount, etch rate, and/or selectivity may gradually increase. When the temperature may continue to increase, the etchants may be desorbed from the substrate surface or may not be easily adsorbed to the surface, which in turn may lead to a decreased etch amount, etch rate, and/or selectivity. Depending on the applications, the temperature within the processing chamber may be maintained between about 30° C. and about 85° C., between about 40° C. and about 80° C., between about 50° C. and about 75° C., or between about 60° C. and about 70° C., to obtain high etch rate and/or selectivity.

In addition to achieving desired etch rate and/or selectivity, the temperature of the processing chamber may be maintained or selected to achieve uniform etching. As discussed above, the trenches 405 in the processed structure 400 shown in FIGS. 4A and 4B may have very high aspect ratios. To achieve uniform etching from the top to the bottom of the trenches 405, also called a 1:1 ratio of top-to-bottom loading, the temperature within the processing chamber may be maintained relatively low. In some embodiments, the temperature may be maintained below about 125° C., below about 100° C., below about 95° C., below about 90° C., below about 85° C., or lower. In some embodiments, by maintaining the temperature between about 30° C. and about 85° C., a 1:1 ratio of top-to-bottom loading may be achieved.

Further, by adjusting the temperature of the processing chamber, the recess profile of each layer of silicon nitride etched may be tuned. In some embodiments, when the temperature of the processing chamber may be maintained between about 30° C. and about 85° C., a relatively straight, and in some embodiments substantially straight, etch profile or recess profile of the recessed sidewalls 430 as shown in FIG. 4B may be obtained. In some embodiments, when the processing chamber may be maintained at relatively lower temperatures, such as below or about 30° C., a convex profile of the recessed sidewalls 430 as shown in FIG. 7A may be obtained. The lower the temperature may be maintained, the more convex profile may result. Without intending to be bound to any particular theory, the convex profile may be formed because the corners as defined by the recessed sidewalls 430 and the adjacent layers of the silicon oxide 420 may generally provide lower-energy adsorption sites for the etchants, and when the temperature may be maintained relatively low, the adsorbed etchants may be less likely to move or become desorbed, resulting in more silicon nitride etched at the corners.

Other processing conditions, such as the pressure within the processing chamber, may also affect the etch profile of the recessed sidewalls of the silicon nitride layers. In some embodiments, when the pressure of the processing chamber may be maintained relatively low, such as below or about 1 Torr, the convex profile of the recessed sidewalls 430 as shown in FIG. 7A may be obtained. When the pressure of the processing chamber may be maintained higher than about 1 Torr, such as above or about 5 Torr, a concave profile of the recessed sidewalls 430 as shown in FIG. 7B may be achieved. When the pressure of the processing chamber may be maintained between about 1 Torr and about 5 Torr or between about 2 Torr and about 4 Torr, the relatively straight etch profile of the recessed sidewalls 430 may be achieved. In some embodiments, when the pressure of the processing chamber may be maintained at about 3 Torr, the etch profile of the recessed sidewalls 430 may be substantially straight as shown in FIG. 4B. Accordingly, depending on the application and the desired recess profile, the pressure within the processing chamber may be maintained at any suitable level between about 0.5 Torr and about 50 Torr. For example, the pressure within the processing chamber may be maintained between about 0.5 Torr and about 1 Torr to achieve a convex recess profile of silicon nitride, the pressure within the processing chamber may be maintained between about 1 Torr and about 5 Torr to achieve a relatively straight recess profile, and the pressure within the chamber may be maintained between about 5 Torr and about 50 Torr to achieve a concave recess profile. The pressure may also be maintained at any pressure within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges.

FIGS. 8A and 8B illustrate the tunability of the selectivity of silicon nitride relative to silicon oxide. In the embodiments shown in FIGS. 8A and 8B, the halogen-containing precursor includes nitrogen trifluoride, and the hydrogen-containing precursor includes diatomic hydrogen, although similar trends or relationships may be observed when other halogen-containing precursors or other hydrogen-containing precursors, such as hydrogen fluoride, may be used. The exposed silicon nitride may include plasma enhanced silicon nitride, low pressure silicon nitride, silicon nitride deposited using ALD, etc., and the exposed silicon oxide may include thermal oxide. Because low pressure silicon nitride may include a greater density and/or strength, and/or a lesser amount of impurities in the film deposited, it may be difficult to achieve selective etching of low pressure silicon nitride relative to silicon oxide using conventional etching methods. The methods described herein may selectively etch various types of silicon nitride to silicon oxide, including selectively etching low pressure silicon nitride relative to silicon oxide, and may achieve a selectivity of low pressure silicon nitride to silicon oxide greater than 1:1, greater than or about 1.1:1, greater than or about 1.2:1, greater than or about 1.3:1, greater than or about 1.4:1, greater than or about 1.5:1, greater than or about 1.6:1, greater than or about 1.7:1, greater than or about 1.8:1, greater than or about 1.9:1, greater than or about 2:1, or greater.

The flow rate of the halogen-containing precursor may be maintained between about 10 sccm and about 2000 sccm, and the flow rate of the hydrogen-containing precursor may be maintained between about 10 sccm and about 2000 sccm. Additionally, by adjusting the ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor, different selectivity may be achieved. Accordingly, the methods described herein may allow for tunability of the selectivity of silicon nitride to silicon oxide. In some embodiments, by adjusting the flow rate ratio of the halogen-containing precursor to the hydrogen-containing precursor between about 1:1 and about 1:3, the selectivity of silicon nitride to silicon oxide may be tuned from greater than 1:1 to about 2:1 or greater, such as from about 1:1 to about 1.8:1. Furthermore, the methods described herein may allow for tunability of the selectivity of silicon nitride to silicon oxide at different temperatures. In the embodiment shown in FIG. 8A, the temperature of the processing chamber may be maintained at about 30° C. When the temperature of the processing chamber may be increased, such as increased to about 60° C. in the embodiment shown in FIG. 8B, the selectivity may also be tunable. By adjusting the flow rate ratio of the halogen-containing precursor to the hydrogen-containing precursor between about 1:1 and about 1:9, the selectivity of silicon nitride to silicon oxide may be tuned from greater than 1:1 to about 2:1 or greater, such as from about 1.2:1 to about 1.5:1. Although 30° C. and 60° C. are described as exemplary operating temperatures, tunability of the selectivity may be achieved at other temperatures, such as below about 30° C., between about 30° C. and about 60° C., above about 60° C., or other temperatures or temperature ranges. Similar to silicon nitride deposited using lower pressure deposition techniques, the methods described herein may also allow the selectivity of silicon nitride deposited using atomic layer deposition to be tuned from 1:1 to 2:1 or greater by adjusting the flow rate ratio of the precursors at various temperatures, such as below about 30° C., between about 30° C. and about 60° C., above about 60° C., or other temperatures or temperature ranges.

FIG. 9 illustrates the relationship between the etch amounts of various materials and the flow rate of the hydrogen-containing precursor. In the embodiments shown in FIG. 9, the halogen-containing precursor includes nitrogen trifluoride, and the hydrogen-containing precursor includes diatomic hydrogen, although similar trends or relationships may be observed when other halogen-containing precursors or other hydrogen-containing precursors, such as hydrogen fluoride, may be used. As shown in FIG. 9, the methods described herein may not only selectively etch silicon nitride relative to silicon oxide, but may also selectively etch silicon nitride relative to silicon, including polysilicon. Specifically, when the flow rate ratio of the halogen-containing precursor to the hydrogen-containing precursor may be adjusted from about 1:1 or less to about 1:3 or greater to obtain various etch amounts of silicon nitride, substantially no etching of polysilicon may occur. Further, when the flow rate ratio of the halogen-containing precursor to the hydrogen-containing precursor may be maintained close to about 1:1, such as between about 1:1 and about 1:1.3, both the etching of silicon oxide and polysilicon may be suppressed, and the methods may selectively etch various silicon nitrides, including silicon nitride deposited using plasma enhanced deposition, lower pressure deposition, atomic layer deposition, or other useful deposition techniques, relative to silicon oxide and polysilicon.

FIG. 10 shows exemplary operations in a method 1000 according to some embodiments of the present technology for selectively etching silicon oxide relative to silicon nitride. Method 1000 may be initiated by providing a halogen-containing precursor at operation 1005 to the processing region of a processing chamber where a substrate or processed structure may be housed. The substrate may include exposed nitride, such as silicon nitride, and exposed oxide, such as silicon oxide. At operation 1010, a hydrogen-containing precursor may be provided to the processing region. At operation 1015, the halogen-containing precursor and the hydrogen-containing precursor may modify and interact with the exposed silicon oxide to form volatile substances, such as ammonium fluorosilicate, which may then be removed from the chamber. The halogen-containing precursor and the hydrogen-containing precursor may not react with the exposed silicon nitride or the reaction may be limited. Accordingly, method 1000 may selectively remove the exposed silicon oxide relative to the exposed silicon nitride.

The halogen-containing precursor used in method 1000 may include a fluorine-containing precursor. An exemplary fluorine-containing precursor may include nitrogen trifluoride (NF₃) and/or hydrogen fluoride (HF). Other sources of fluorine may be used in conjunction with or as replacements for nitrogen trifluoride and/or hydrogen fluoride. In some embodiments, the fluorine-containing precursor may include at least one precursor selected from the group of atomic fluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride, hydrogen fluoride, xenon difluoride, and various other fluorine-containing precursors used or useful in semiconductor processing. The precursor may also include any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful gases.

The hydrogen-containing precursor used in method 1000 may include ammonia (NH₃). Other sources of hydrogen may be used in conjunction with or as replacements for ammonia. In some embodiments, the hydrogen-containing precursor may include at least one precursor selected from the group of ammonia, a hydrocarbon, an alcohol, hydrogen peroxide, and various other hydrogen-containing containing precursors used or useful in semiconductor processing. The precursor may also include any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful gases.

In some embodiments, both the halogen-containing precursor and the hydrogen-containing precursor may be flowed into a remote plasma region of the processing chamber to form plasma effluents of the halogen-containing precursor and the hydrogen-containing precursor. In some embodiments, only one of the halogen-containing precursor and the hydrogen-containing precursor may be provided to the remote plasma region to form plasma effluents, and the other one of the halogen-containing precursor and the hydrogen-containing precursor may bypass the remote plasma region and may be provided into the processing region without forming a plasma thereof. In some embodiments, both the halogen-containing precursor and the hydrogen-containing precursor may bypass the remote plasma region, and the precursors may be provided to the processing chamber without forming plasma effluents of either precursor. Consequently, depending on the implementation, the precursors provided to the processing region of the processing chamber in method 1000 may include plasma effluents of both the halogen-containing precursor and the hydrogen-containing precursor, plasma effluents of only one of the halogen-containing precursor and the hydrogen-containing precursor, or no plasma effluents. Whether or not a plasma may be formed from the halogen-containing precursor and/or the hydrogen-containing precursor, method 1000 may selectively etch silicon oxide relative to the silicon nitride.

Additionally, the selectivity of silicon oxide to silicon nitride may be tuned by adjusting one or more of the flow rate ratio, temperature, pressure, and other operating conditions. In some embodiments, when the ratio of the flow rate of the halogen-containing precursor to the flow rate of the hydrogen-containing precursor may be maintained at between about 1:2 and about 1:3, such as about 1:2.5, the etching of silicon nitride may be substantially suppressed. Method 1000 may have a selectivity of silicon oxide relative to silicon nitride greater than or about 20:1, greater than or about 30:1, greater than or about 40:1, greater than or about 50:1, greater than or about 60:1, greater than or about 70:1, greater than or about 80:1, greater than or about 90:1, greater than or about 100:1, greater than or about 110:1, greater than or about 120:1, greater than or about 130:1, greater than or about 140:1, greater than or about 150:1, or greater.

The temperature of the processing chamber may be maintained between about 0° C. and about 150° C. to achieve the high selectivity of silicon oxide to silicon nitride. In some embodiments, the temperature of the processing chamber or at the substrate level may be maintained below or about 150° C., below or about 100° C., below or about 60° C., below or about 50° C., below or about 40° C., below or about 35° C., below or about 30° C., below or about 25° C., below or about 20° C., below or about 15° C., below or about 10° C., below or about 5° C., below or about 0° C., or lower, while maintaining a selectivity of silicon oxide over silicon nitride greater than or about 30:1, greater than or about 50:1, greater than or about 70:1, greater than or about 80:1, greater than or about 90:1, greater than or about 100:1, or greater. Further, the selectivity may be maintained or may not decrease over time. Method 1000 may achieve and/or maintain the high selectivity of silicon oxide to silicon nitride even when the operations may be performed at relatively low temperatures, such as at about 10° C. or lower. Method 1000 may also maintain the etch rate of silicon nitride with time. As shown in FIG. 11, the etch amount of silicon oxide may increase over time and may be substantially linearly dependent on the etch time in some embodiments. In contrast, the etching of silicon nitride may be substantially suppressed or may not increase significantly as the etching of silicon oxide may be continued. Consequently, the etch selectivity of silicon oxide to silicon nitride may be maintained and may not decrease as the etching of silicon oxide may be continued.

The pressure within the processing chamber may be maintained between about 0.5 Torr and about 50 Torr. In some embodiments, the pressure within the processing chamber may be maintained below or about 40 Torr, below or about 30 Torr, below or about 20 Torr, below or about 10 Torr, below or about 5 Torr, below or about 4 Torr, below or about 3 Torr, below or about 2 Torr, below or about 1 Torr, below or about 0.5 Torr, or lower. The pressure may also be maintained at any pressure within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges.

The various etching methods described herein offer many advantages. Methods described herein may use gas etchants to reach the bottom of trenches in a 3D NAND structure or other features that may have high aspect ratios, thereby improving etch uniformity or the top to bottom loading as compared with conventional wet etching processes. The byproduct formed from the methods described herein may be volatile, and thus may be easily removed by increasing or maintaining the temperature of the processing chamber and/or the substrate at or above about 125° C., leaving substantially no residual byproduct or less residual byproduct as compared to conventional wet processes. Further, the methods described herein may provide the capability of tuning the etched recess profile, such as the recess profile of the etched silicon nitride, to achieve a convex, straight, and/or concave recess profile. The methods described herein may also provide the capability of tuning the selectivity of silicon nitride and/or silicon oxide. By selecting the precursors, and/or adjusting the flow rate ratios of the precursors, the temperature of the processing chamber, and/or the pressure within the processing chamber, the methods may selectively etch nitride relative to oxide in some embodiments, or may selectively etch oxide relative to nitride in other embodiments. Depending on the precursors and/or operating conditions, the methods may achieve a nitride-to-oxide selectivity from about 1:1 to about 500:1 or greater in some embodiments, and may achieve an oxide-to-nitride selectivity from about 1:1 to about 100:1 or greater in other embodiments. By using a halogen-containing precursor and a hydrogen-containing precursor, the methods described herein may generally achieve a higher selectivity as compared to etching methods where oxygen-containing precursors may be used.

In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. Additionally, methods or processes may be described as sequential or in steps, but it is to be understood that the operations may be performed concurrently, or in different orders than listed.

Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a precursor” includes a plurality of such precursors, and reference to “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups. 

1. An etching method comprising: flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber; forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor; flowing the plasma effluents into a processing region of the semiconductor processing chamber, wherein the processing region houses a substrate, wherein the substrate comprises a high-aspect-ratio feature, and wherein the substrate further comprises a region of exposed silicon nitride and a region of exposed oxide; providing a hydrogen-containing precursor into the processing region of the semiconductor processing chamber; and selectively removing at least a portion of the exposed silicon nitride relative to the exposed oxide.
 2. The etching method of claim 1, wherein the hydrogen-containing precursor bypasses the remote plasma region when provided to the processing region.
 3. The etching method of claim 1, wherein the fluorine-containing precursor comprises nitrogen trifluoride.
 4. The etching method of claim 1, wherein the hydrogen-containing precursor comprises one of diatomic hydrogen or hydrogen fluoride.
 5. The etching method of claim 1, wherein the hydrogen-containing precursor is oxygen-free.
 6. The etching method of claim 1, wherein a ratio of a flow rate of the fluorine-containing precursor to a flow rate of the hydrogen-containing precursor ranges between about 1:10 and about 2:1.
 7. The etching method of claim 1, wherein a temperature of the substrate is maintained between about 0° C. and about 150° C. during the etching method.
 8. The etching method of claim 1, wherein a pressure within the semiconductor processing chamber is maintained between about 0.5 Torr and about 50 Torr.
 9. The etching method of claim 1, wherein the etching method has a selectivity of silicon nitride to oxide greater than or about 500:1.
 10. The etching method of claim 1, wherein the etching method produces a recessed sidewall of the exposed silicon nitride, and wherein the recessed sidewall has a substantially straight recess profile.
 11. The etching method of claim 1, wherein the exposed oxide comprises silicon oxide.
 12. The etching method of claim 1, wherein the substrate further comprises a region of exposed silicon, and wherein the portion of the exposed silicon nitride is further selectively removed relative to the exposed silicon.
 13. An etching method comprising: flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber; forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor; flowing the plasma effluents into a processing region of the semiconductor processing chamber, wherein the processing region houses a substrate, wherein the substrate comprises a trench formed between two vertical columns, and wherein each of the two vertical columns comprises alternating layers of silicon nitride and an oxide material; while flowing the fluorine-containing precursor into the processing region, providing a hydrogen-containing precursor to the processing region to produce an etchant; and selectively removing at least a portion of silicon nitride from each layer of silicon nitride with the etchant.
 14. The etching method of claim 13, wherein a temperature of the substrate is maintained between about 30° C. and about 85° C. during the etching method.
 15. The etching method of claim 13, wherein a pressure within the semiconductor processing chamber is maintained between about 1 Torr and about 5 Torr.
 16. The etching method of claim 13, wherein a ratio of a flow rate of the fluorine-containing precursor to a flow rate of the hydrogen-containing precursor is greater than or about 1:2.
 17. The etching method of claim 13, wherein the substrate comprise a region of exposed silicon, and wherein the portion of silicon nitride from each layer of silicon nitride is selectively removed relative to the exposed silicon.
 18. The etching method of claim 13, wherein the oxide material comprises silicon oxide.
 19. A removal method comprising: flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber; forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor; flowing a hydrogen-containing precursor into the remote plasma region of the semiconductor processing chamber; forming a plasma within the remote plasma region to generate plasma effluents of the hydrogen-containing precursor; flowing the plasma effluents of the fluorine-containing precursor and the plasma effluents of the hydrogen-containing precursor into a processing region of the semiconductor processing chamber, wherein the processing region houses a substrate, wherein the substrate comprises a high-aspect-ratio feature, and wherein the substrate further comprises a region of exposed silicon nitride and a region of exposed silicon oxide; and selectively removing at least a portion of the exposed silicon nitride relative to the exposed silicon oxide.
 20. The removal method of claim 19, wherein the substrate further comprises a region of exposed silicon, and wherein the portion of the exposed silicon nitride is removed relative to the exposed silicon. 